1. Field of the Invention
This invention relates to hot melt release coatings and, in particular, to hot melt processes for producing release coatings for linerless and linered labels.
2. Description of Related Art
Pressure sensitive adhesive labels conventionally include a pressure sensitive adhesive (PSA) material coated onto a substrate with a release layer affixed thereto. The release layer may be coated onto another substrate, a liner, which is then affixed to the adhesive substrate. Such labels, called linered labels, are used by simply peeling away the release liner and pressing the adhesive coated side of the substrate to the desired surface. The liner acts as a support for transport, printing and storage, and is discarded after the substrate coated with the PSA is removed from the liner. In contrast, a linerless label has a face surface that is coated with a release coating and a back surface that is coated with a PSA. A strip of linerless labels may be wound in a roll configuration so that the PSA on the back side of the strip is in contact with the release coating on the face side of the strip, where the release coating faces outwardly. The adhesion between the PSA and release coating holds the strip in a roll. Labels made in this way can be peeled off individually from the roll of linerless labels, without having a liner web to tear off and discard each time a label is used.
Various release coatings have been proposed for use with linerless and linered labels. A desired release material is one that is receptive to printing and also has good release properties. It has been found, however, that while certain release compositions provide adequate release properties for pressure sensitive adhesives, they are either not receptive to printing or the printing is removed from the release when the PSA is removed from its liner or from a roll.
Moreover, many release compositions include potentially flammable and toxic solvents, which create problems in use. Solvents need to be removed by drying, which is not only an additional costly step in the process, but also causes removal of moisture from paper, resulting in undesirable wrinkling or curling. Such wrinkling or curling, in linered labels, can cause the release coating to become detached from the PSA layer. Also, when solvents are removed from the release composition, the coated substrate can take on a cloudy or dirty appearance, which is undesirable, particularly for linerless labels in which the release stays with the label and is not discarded.
Thus, there is a need for a release coating that provides adequate release properties for pressure sensitive adhesives, and also allows ink to adhere to the release surface.
There is also a need for a release coating that does not contain solvents and thus can be applied without a drying step.
There is also a need for a release coating that provides a high gloss finish.
There is a further need for a release coating that provides good barrier properties.
There is a further need for a release that can be spot coated onto a portion of a substrate.
The present invention satisfies these and other needs by providing a release coating applied by a hot melt process that does not require solvents or a drying step, has a high gloss finish, can be easily spot coated, and provides good barrier properties.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.